Objective: Mental illnesses exacerbate the disability associated with physical disorders and complicate their management, making persons with co-occurring mental illnesses such as depression particularly vulnerable to suboptimal quality of care. This intersection between psychiatric co-morbidity and chronic conditions may also be exacerbated among racial minorities. The patient-centered medical home (PCMH) model is an increasingly popular method to improve quality of care for this complex population. But while the rationale for PCMH transformation is well-documented, different patient populations may not benefit equally from this model, and the effect of PMCH on racial disparities in quality of care is unknown. The objective of this study is to investigate the effects of the PCMH model on disparities in quality of care among populations with co-morbid depression and chronic physical conditions. Methods: Using 2008-2012 Medicaid claims merged with practice-level data on NCQA-recognized PCMHs, aim 1 of this study will compare racial/ethnic disparities in quality of care for adults with depression and co- morbid physical conditions who are enrolled in a PCMH to their counterparts receiving usual primary care under Medicaid. Outcomes analyzed will include claims-based disease-specific quality measures for depression and chronic physical conditions. The analysis will control for selection into the PCMH using county rates of PCMH adoption as an instrumental variable. Aim 2 will use provider-level fixed effects and the same mental health and physical health quality indicators as aim 1 to assess variations in quality of care for Medicaid-enrolled adults receiving care in PCMHs with differing levels of NCQA recognition (levels 1, 2, or 3). Finally, aim 3 will use a person-centered treatment (PeT) effects model to understand heterogeneity of individual-level treatment effects among diverse subpopulations of PCMH enrollees, including the intersecting effects of age, gender, rurality, and number of co-morbid conditions. Contribution and Significance: This project will generate new knowledge on the potential of the PCMH to reduce racial/ethnic disparities in care and provide a more detailed understanding of which patients benefit the most from the PCMH model. The proposed research will focus on racial minorities, low-income individuals, and patients requiring complex chronic care, all populations identified by AHRQ as high-priority. The findings from this study will be useful for policymakers and health administrators considering or currently implementing the PCMH model, especially for racially diverse populations and for patients with co-morbid mental and physical illness.